/**
 * Copyright (C) 2015 MongoDB Inc.
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * As a special exception, the copyright holders give permission to link the
 * code of portions of this program with the OpenSSL library under certain
 * conditions as described in each individual source file and distribute
 * linked combinations including the program with the OpenSSL library. You
 * must comply with the GNU Affero General Public License in all respects
 * for all of the code used other than as permitted herein. If you modify
 * file(s) with this exception, you may extend this exception to your
 * version of the file(s), but you are not obligated to do so. If you do not
 * wish to do so, delete this exception statement from your version. If you
 * delete this exception statement from all source files in the program,
 * then also delete it in the license file.
 */

#pragma once

#include <string>
#include <vector>

namespace mongo {

/**
 * DNS canonicalization converts a hostname into another potentially more globally useful hostname.
 *
 * This involves issuing some combination of IP and name lookups.
 * This enum controls which canonicalization process a client will perform on a
 * hostname it is canonicalizing.
 */
enum class HostnameCanonicalizationMode {
    kNone,              // Perform no canonicalization at all
    kForward,           // Perform a DNS lookup on the hostname, follow CNAMEs to find the A record
    kForwardAndReverse  // Forward resolve to get an IP, then perform reverse lookup on it
};

/**
 *  Returns zero or more fully qualified hostnames associated with the provided hostname.
 *
 *  May return an empty vector if no FQDNs can be determined, or if the underlying
 *  implementation returns an error. The returned information is advisory only.
 */
std::vector<std::string> getHostFQDNs(std::string hostName, HostnameCanonicalizationMode mode);

}  // namespace mongo
